Originally posted Mar 10, 2014
Sometimes less is more. But sometimes more is more. And better, too.
The term “big data” has certainly been over-hyped but there is something useful in the concept, in a variety of applications. In this post I’ll show a non-faddish example of how a big data view can increase both productivity and insight for RF engineers.
Before I go further, however, I’ll offer my definition of big data in this context: I’m referring to a situation in which you pull together many pieces and types of information, aiming to see them all at once, discover relationships and get actionable insight. The payoff is that you’ll discover phenomena and understand relationships that you might otherwise miss. It’s a way of leveraging your own engineering skills to improve productivity and reduce the risk of missing problems or settling on a suboptimal solution.
Defined this way, big data can be just the thing for design and troubleshooting in wireless systems. These jobs demand multi-measurement views and analysis because of their complex multi-factor nature, with one type of complexity piled on another and another to an amazing degree.
For example, OFDM systems use multiple subcarriers that can independently carry different types of modulation and can change modulation type after every symbol. Power levels can vary between subcarriers and can change at every symbol. Multiple channels can be used and may carry entirely separate data streams or coded versions of the same stream. Multiple users may be supported by beam forming or multiplexing schemes. Multiple frequency allocations may be aggregated, and reallocated on a dynamic basis. Multiple radios may be used at the same time on the same device, competing for power and processor cycles. The list goes on, with each factor multiplying the complexity of the total task.
Fortunately, our eye-brain system is wired to handle this multiplicity, perhaps better than we realize. We can view multiple data sets on the same trace as I described in the post Spectrum analysis and the opposite of data reduction, and we can view many different traces on the same display as shown in the example below.
Sixteen measurements of a single LTE signal are shown on one Agilent 89600 VSA display. Frequency-, time- and modulation-domain results are related to each other in an arrangement that can be completely customized to spot problems and optimize analysis (click on the figure to view at full size).
Large, inexpensive monitors are available for both PCs and benchtop instruments such as Agilent’s X-Series signal analyzers. An ordinary 1920×1080 screen has nearly twice the pixels of the example shown here, and the tools in the 89600 VSA allow you to configure a display that makes effective use of the powerful pattern recognition and system knowledge you already have.
In the past I’ve described how the right view can make an obscure problem obvious and how a different view can do the same for a different problem, demonstrating that some defects that are obscure in one measurement or domain are obvious in another. By using many simultaneous measurements you’ll maximize the chances that a problem will be clearly revealed in one of them.
There is one more benefit to a large, multi-window display—or even two displays—particularly with the 89600 VSA and demodulation: There are many signal and modulation parameters you may adjust, and you can bring up multiple control windows at the same time, easily switching between them to make the changes you want without the need to close one control and open another.
A big display with lots of measurements won’t make you omniscient but it will move you in that direction!